The invention relates to propylene polymer-based hot melt adhesive compositions.
Hot melt adhesive compositions are often used to bond two substrates together and are applied in a molten state to at least one of the substrates. To be commercially viable, most hot melt adhesive compositions must maintain adhesion to the substrate at room temperature.
For an adhesive composition to be suitable for use in high speed packaging operations, the adhesive must exhibit a fast set time and a fiber tearing bond. It is very difficult to achieve these properties when the hot melt adhesive composition is based on a propylene polymer. Waxes are often used in an attempt to improve set time; however, waxes often have a deleterious effect on adhesion. Polyethylene-based and Fischer Tropsch waxes, for example, tend to be incompatible with propylene-based hot melt adhesive compositions and tend to phase separate from the propylene polymer as the composition cools, which results in poor adhesion.
In the past, hot melt adhesive compositions have been formulated with LINXAR 127 propylene-hexene copolymer, which had been produced by ExxonMobil Chemical Company (Houston, Tex.). However, LINXAR 127 is no longer commercially available. Accordingly, there is a need to formulate hot melt adhesive compositions that are based on propylene polymers other than LINXAR 127, and that exhibit both a fast set, time and good fiber tearing adhesive properties. There is also a need to improve the set time of hot melt adhesive compositions that are based on propylene polymers whether that polymer is LINXAR 127 or another propylene polymer.